The primary purpose of histones in DNA structure is to facilitate the packaging and organization of DNA within the nucleus of eukaryotic cells. Histones are proteins that bind to DNA, forming a complex known as chromatin. This complex allows long strands of DNA to be condensed into a compact structure, which is necessary for cell division and proper gene expression. Histones also play a key role in the regulation of gene activity, influencing transcription and the cell’s ability to respond to environmental changes, thus ensuring cellular functionality.